Factory Price Hot Rolled Forged Steel Bar 42CrMo SAE 1045 4140 4340 8620 8640 Alloy Steel Round Bars

• Customization: Available
• Type: Round
• Standard: AISI, ASTM, DIN, JIS, GB, BS
• Technique: Forged
• Shape: Plate
• Surface Treatment: Polished
• Special Use: High-strength Steel Plate, Wear Resistant Steel, Silicon Steel, Cold Heading Steel, Free Cutting Steel, Mold Steel
• Application: Tool Steel Bar
• Surface: Milled/Bright/Black
• Length: 1-10m
• Transport Package: Wooden
• Specification: 6-400mm
• Trademark: Smooth
• Origin: China
• HS Code: 7214100000
• Production Capacity: 5000 Ton/Year

Product Description

Introduction:  

AISI 4340 steel Manufacturer and Exporter,supplied with round,square,flat,block,and shaft etc.AISI 4340 is defined as a heat treatable and low alloy steel which has 0.8% Cr, 0.2% Mo and 1.8% Ni as strengthening alloy elements.Compared with AISI 4140,it has higher strength and toughness,also it has very good fatigue resistance, wear resistance and atmospheric corrosion resistance.AISI  4340 is generally supplied in  hardened and tempered condition with the tensile range of 930 - 1080 Mpa ,hardness 280-320HB.Pre hardened and tempered 4340 can be further surface hardened by flame or induction hardening and by nitriding.

1.Supply Form & Size & Tolerance

Supply Form	Size(mm)	Process	Tolerance
Round	Φ6-Φ100	Cold Drawn	Bright/Black	Best H11
	Φ16-Φ350	Hot Rolled	Black	-0/+1mm
			Peeled/ground	Best H11
	Φ90-Φ1000	Hot Forged	Black	-0/+5mm
			Rough Turned	-0/+3mm
Flat/Square/Block	Thickness :120-800	Hot Forged	Black	-0/+8mm
	Width:120-1500		Rough Machined	-0/+3mm

Remark:Tolerance can be customized as per requests
2.Chemical Composition

Standard	Grade	C	Si	Mn	P	S	Cr	Ni	Mo
ASTM A29	4340	0.38-0.43	0.15-0.35	0.6-0.8	≤ 0.035	≤ 0.04	0.7-0.9	1.65-2.0	0.2-0.3
EN10250	36CrNiMo4	0.32-0.4	≤ 0.4	0.5-0.8	≤ 0.035	≤ 0.035	0.9-1.2	0.90-1.2	0.15-0.3
	1.6511
BS 970	EN24	0.36-0.44	0.1-0.4	0.45-0.7	≤ 0.035	≤ 0.04	1.0-1.4	1.3-1.7	0.2-0.35
	817M40
JIS G4103	SNCM439	0.36-0.43	0.15-0.35	0.6-0.9	≤ 0.03	≤ 0.03	0.6-1.0	1.6-2.0	0.15-0.3
GB 3077	40CrNiMoA	0.37-0.44	0.17-0.37	0.5-0.8	≤ 0.025	≤ 0.025	0.6-0.9	1.25-1.65	0.15-0.25

3.Physical Property

Density g/cm3	7.85
Melting point °C	1427
Poisson's ratio	0.27-0.30
Machinability (AISI 1212 as 100% machinability)	50%
Thermal expansion co-efficient µm/m°C	12.5
Thermal conductivity W/(m.K)	44.5
Modulus of elasticity 10^3 N/mm^2	210
Electric resistivity Ohm.mm2 /m	0.19
Specific heat capacity J/(kg.K)	460
Modulus of elasticity 10^3 N/mm2	100 ºC	200 ºC	300 ºC	400 ºC	500 ºC
	205	195	185	175	165
Thermal expansion 10^6 m/(m.K)	100 ºC	200 ºC	300 ºC	400 ºC	500 ºC
	11.1	12.1	12.9	13.5	13.9

4. Mechanical Property

Mechanical Condition	T	U	V	W	X	Y	Z
Ruling Section (mm)	150	100	63	30	30	30	30
Tensile Strength Mpa	850-1000	930-1080	1000-1150	1080-1230	1150-1300	1230-1380	>1550
Yield Strength,Mpa	≥665	≥740	≥835	≥925	≥1005	≥1080	≥1125
Elongation %	≥13	≥12	≥12	≥11	≥10	≥10	≥5
Izod Impact J	≥54	≥47	≥47	≥41	≥34	≥24	≥10
Charpy Impact J	≥50	≥42	≥42	≥35	≥28	≥20	≥9
Brinell Hardness HB	248-302	269-331	293-352	311-375	341-401	363-429	>444

5.High Temperature Strength

For quenched and tempered heavy forgings
Diameter mm	Yield strength MPa
	20 ºC	100 ºC	200 ºC	250 ºC	300 ºC	350ºC	400ºC
≤250	590	549	510	481	441	412	371
250-500	540	505	471	451	412	383	353
500-750	490	466	441	422	392	363	343

6.Forging
Forging temperature should be carried out between 1150ºC-1200ºC,The lower the forging-ending temperature ,the finer the grain size .hold suitable time for the steel to be thoroughly heated before forge, but don't forge below minimum forging temperature 850°C. AISI 4340 has good forging characteristics,but crack is easily occured when improper cooling way after forged,so it  should be cooled as slowly as possible in still air or in sand after forged.
7.Normalizing
Normalizing is used to refine the structure of forgings that might have cooled non-uniformly after forged,and considered as a conditioning treatment before final heat treatment.Normalizing temperature for AISI 4340 steel should be carried out between 850ºC-880ºC. hold suitable time for the steel to be thoroughly heated to complete the ferrite to austenite transformation.Cool in still air.
8.Annealing
Full annealing is recommended  for AISI 4340 before machining, AISI 4340 should be carried our at a nominal temperature of 830ºC-850ºC,hold suitable time for the steel to be thoroughly heated, then furnace cooling to 610ºC at a rate of 11ºC per hour, finally air cooling.
9.Hardening
This heat treatment will obtain martensite structure after quenched.It will  increase the surface hardness and strength.AISI 4340 should be carried out between 830ºC-865ºC, hold suitable time for the steel to be thoroughly heated, soak for 10-15 minutes per 25 mm section, oil quench is recommended.Tempering should be followed  immediately after quenched.
10.Tempering
AISI 4340 alloy steel should be in the heat treated or normalized and heat treated condition before tempering.Tempering is usually carried out to relieve stresses from the hardening process, but primarily to obtain the required  hardness and mechanical properties. The actual tempering temperature will be chosen to meet the required properties.it is usually carried out at 450ºC- 660ºC,hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section, and cool in still air.Tempering between 250ºC-450ºC is not avoided as tempering within this range will seriously reduce the impact value,result in temper brittleness.
11.Application
AISI 4340 is often used in preference to AISI 4140 at the higher strength levels because of its better hardenability and improved CVN impact toughness.
Typical applications include:Heavy-duty axles, shafts, heavy-duty gears,spindles, pins, studs, collets, bolts, couplings,sprockets, pinions, torsion bars, connecting rods,crow bars, conveyor parts,forged hydraulic,forged steel crankshafts etc.